The Global System for Mobile Communication (GSM) is one of the most widely deployed communication standards for mobile wireless communication. As an extension of GSM in order to introduce packet-switched technology. General Packet Radio Service (GPRS) was developed by the European Telecommunications Standards Institute (ETSI). One limitation of GPRS is that it does not support voice services. Therefore, the Third Generation Partnership Project (3GPP) has developed a new standard for GSM to support high rate data services. This standard is known as Enhanced Data Rates for Global Evolution (EDGE).
A network according to these standards comprises a core network (CN), radio access networks (RAN) and mobile stations (MS) attached to a RAN, such as the GSM/EDGE Radio Access Network (GERAN) architecture. The GERAN comprises a plurality of base station systems (BSS) and each of these BSSs comprises a base station controller (BSC) and a set of base transceiver stations (BTS).
In a BSS system where the radio link control/medium access control (RLC/MAC) protocol is centralized, the physical layer latency (e.g. packet transfer and serialization delays) easily becomes a vital part of the total latency consequently adding end-to-end delays for packet switched traffic.
A centralized RLC/MAC Protocol needs to maintain synchronization over the physical layer at all times. This is critical to maintain the RLC/MAC Scheduler synchronized with the BTS.
A GPRS/EDGE BSS system must also be able to handle transmission network congestion, micro-link induced packet losses, satellite link delays, busy hours load etc., etc. The conclusion is that in order to efficiently handle permanent and variable delays and at the same time provide optimal GPRS/EDGE performance, a self regulated physical layer would be desired.